The present invention relates to a percussion or impact tool, such as an electrically operated hammer, which comprises an intermediate member for transmitting a reciprocative movement of a striking member to a tool bit positioned at a front end of the percussion tool.
An air spring is conventionally used to cause the striking member to reciprocate. The intermediate member receives the percussion energy caused by the reciprocative movement of the striking member, and transmits the percussion energy to the tool bit to cause the percussive motion of the tool bit in the axial direction. The percussive movement of the tool bit is directly transmitted to a concrete or similar material to be drilled or cut, while the tool bit receives a reaction or rebound force acting from the drilled or cut material. In such a loaded condition, the percussion force is effectively transmitted to the drilled or cut material through the transmitting mechanism including the striking member, the intermediate member, and the tool bit.
When a drilling or cutting work is finished, an operator releases the percussion tool from the drilled or cut material. However, immediately after finishing the drilling or cutting operation, the air-spring type percussion tool still operates. The percussion force transmitting mechanism does not immediately stop and continues to transmit the reciprocative movement for a while. Namely, the percussion force transmitting mechanism is suddenly released from the loaded condition and left in a non-loaded condition. The percussion force is no longer transmitted to the drilled or cut material and must be absorbed by the percussion tool itself. In this case, there is the possibility that a part of the percussion force transmitting mechanism, e.g., the intermediate member, may excessively hit other parts in the percussion tool and may damage the same.